Side and bottom discharge mine hoppers are well known. The hoppers generally consist of a hopper body which is mounted on a wheeled frame or chassis and include one or more doors for opening and closing an opening at the base of the side wall or walls or in the base of the hopper body. The hopper doors are more often than not held in their closed position by latches which consist of a hook shaped movable part which is engaged with a fixed catch. The latches, in automatic discharge applications, are released by mechanisms on the hoppers which, at the tip at which the hoppers are to be discharged, are activated by some fixed structure at the side of the tip. Examples of latch release mechanisms of this type are disclosed in U.S. Pat. Nos. 1,294,876, 1,378,574, 2,686,479 and South African Pat. No. 85/7110. In a second type of latch arrangement the release mechanisms are located on the underside of the hoppers where they are positioned to engage release structure which is located between or at ground level alongside, the hopper tracks. Examples of these are disclosed in U.S. Pat. Nos. 1,266,630, 1,333,947 and 4,339,222. A first problem with all of the latch arrangements which are disclosed in the above patents is that the hook and catch formations wear fairly rapidly in use due to the large frictional forces imposed on them by the loads against which they have to operate. In underground mining operations the hoppers are, in many mines, loaded with material which contains a high percentage of abrasive slurry which inevitably finds its way onto and into all of the movable mechanisms on the hopper considerably to aggrevate the wear of the above latch components. The latch components when worn firstly do not positively close the hopper doors which then allow the slurry, including what could be highly valuable ore fines, to dribble from the hoppers and secondly and more importantly cause the doors to unlatch unintentionally when the hoppers are banged and jarred in normal tramming operations. Another problem with most of the latch release mechanisms and particularly those which are activated by release arrangements between or adjacent the hopper tracks is accidental discharge of the hoppers when the latch releases are activated by objects such as logs or chunks of rock or coal which are situated between or alongside the hopper tracks. Accidental dsicharge of a hopper, particularly the larger five to eight tonne hoppers causes serious, expensive and often dangerous disruption of mine production as it is no simple task in the confined space of a mine haulage, to clear the hopper track of the disabled hopper and its partially discharged load.
To minimize this problem great care is taken in most mines to ensure that hopper locking arrangements are of a type which will ensure positive locking of the doors even when the latch components become worn or distorted by accidental damage and also that the latch release mechanisms are so positioned on the hoppers that they are well clear of anything between or alongside the hopper tracks which may cause accidental actuation of the door release mechanisms.
In high speed haulages the accidental discharge problem is often compounded by derailment of not only the discharged hopper but also of the hoppers close to it in the train. In many accidents of this type the derailed hoppers have injured mine personnel and seriously damaged mine services located on the haulage walls.